1. Field of the Invention
This invention relates generally to the field of memory controller design and, more particularly, to the design of a temperature throttling mechanism for safe and efficient memory operation.
2. Description of the Related Art
Many digital systems, especially those that include high-performance, high-speed circuits, are prone to operational variances due to temperature effects. Devices that monitor temperature and voltage are often included as part of such systems in order to maintain the integrity of the system components. Personal computers (PC), signal processors and high-speed graphics adapters, among others, typically benefit from such temperature monitoring circuits. For example, a central processor unit (CPU) that typically “runs hot” as its operating temperature reaches high levels may require a temperature sensor in the PC to insure that it doesn't malfunction or break due to thermal problems.
Often, integrated circuit (IC) solutions designed to measure temperature in a system will monitor the voltage across a diode (or multiple diodes) at different current densities to extract a temperature value. This method generally involves amplifying (or gaining up) a small voltage generated on the diode(s), and then subtracting voltage from the amplified temperature-dependent voltage in order to center the amplified (gained) value for conversion by an analog-to-digital converter (ADC). In other words, temperature-to-digital conversion for IC-based temperature measuring solutions is often accomplished by measuring a difference in voltage across the terminals of typically identical diodes when different current densities are forced through the PN junctions of the diodes. The resulting change in the base-emitter voltage between the diodes (ΔVBE) is generally proportional to temperature. While temperature sensors have predominantly been configured on the CPU and/or discrete temperature sending modules, more recently they have begun to be included in other critical system components such as, for example, system memory, which in many systems comprises double data rate synchronous dynamic random access memory (DDR SDRAM, or DDR for short).
Typically, especially in today's ever-faster systems, if left unchecked, memory devices (e.g. DDR) may start running above their maximum operating temperatures, resulting in potential memory-related reliability issues. One procedure to correct for, or to prevent this problem has been to throttle the memory bus to ensure that the memory devices keep operating within their thermal limits. Memory throttling generally provides a solution to cool the memory devices by reducing memory traffic allowed on the memory bus, thereby reducing the power consumed by the memory devices, which leads to reduced thermal output.
While in many cases, semiconductor-based temperature sensing methods are employed to obtain readings corresponding to temperature values, there may be cases when the obtained readings, while related to temperature, do not directly correspond to actual temperature values. For example, signals extracted from temperature sensors configured in memory devices may be used to provide an indication of certain temperature levels having been crossed, without returning actual temperature values. In such cases, an intelligent bus throttling method may be required to maximize system performance while ensuring that the accessed memory devices operate within their specified thermal limits.
Other corresponding issues related to the prior art will become apparent to one skilled in the art after comparing such prior art with the present invention as described herein.